Regulation of electrical circuits



Jan. a, 1928.

1,654,988 A. H. MITTAG REGULATION OF ELECTRICAL cmcuns 2 Sheets-Sheet 2 Original Filed 00t.28, 1925 Patented Jan. 3, 1928.

ALBERT H. MITTAG, OF SCHENECTA'DY,

NEW YORK. ASSIGNOR T GENERAL ELECTRIC COMPANY, A CORI'ORATION OF NEW YORK.

REGULATION OF ELECTRICAL CIRCUITS.

Original application filed October 28, 1925, Serial No. 65,454. Divided and this application filed October 30, 1926.

Myinvention relates to the regulation of electrical machines or circuits, and has ior itsprincipal object the provision of an 1mproved apparatus and method wherebythe electrical conditions of such a machine or circuit may be reliably and sensitively regulated.

Various apparatus have been provided in the past for regulating the voltage or another electrical condition of a machineor circuit. As ointed out in my copendmg application, erial No. 65,454, filed October 28, 1925, many of these apparatus comrise movable contacts or other elements which render them incapable of producing the fine degree of regulation required for stable operation of a machine or circuit under adverse conditions such as those encountered in connection with high voltage grower systems subjected to heavy loads. he present application is a division of the aforesaid copending application and relates more particularl invention where y minimum and maximum 2 corrective efiects are averaged in a manner to ensure pro r regulation under adverse operating con itions.

My invention will be better understood from the following description when considered in connection with the accompanying drawings and its scope will be-pointed out in the appended claims.

Referring to the drawings, Fig. 1 shows a re lating arrangement wherem my mvention has been embodied; Fig. .2 illustrates certain details in the operation of this arrangement; Fig. 3 shows a modified embodiment of the invention; and Fig. 4 illustrates certain details in the operation of the arrangement illustrated by Fig. 3.

Fi 1 shows an electrical machine .1 whi is connected to a load circuit 2 and is provided with a field winding 3 connect ed to this circuit through a transformer 4 and an electrical valve 5 which comprises grid or control electrodes 6 and 7, a mercury cathode 8 and anodes 9 and 10. The valve 5 is provided with a starting switch 11 and battery 12 and is of a type such that the starting of current between its cathode and anodes may be prevented by the application of a negative potential to :lrig'n s 6 and 7. After this current has st howto the embodiments of the Serial No. 145,352.

ever, it persists till the anode voltage passes through its zero value.

The grids 6 and 7 are connected to the cathode 8 through resistors 13 and 14, opposite halves of the secondary circuit 16 of a transformer 17, and a battery 18 by which a positive. bias potential is applied to the grids. The primary circuit 19 of the transformer 17 is connected to the load circuit 2 through a phase control device 20. A source of current shown as a battery 12 may be provided for initiating excitation of the machine 1 if its residual magnetism is insuflicient to produce this result.

The operation of the apparatus will be explained by reference to Fig. 2 wherein the potential of the anode 9 for example is represented by the curve 26,'different values of the potential applied to the grid 6 through the transformer 17 are represented by the curves 27 and 27, and the positive bias potential applied to the grid 6 by the battery 18 is indicated by the line 28. The resultant potential applied to the grid 6 is thus dependent both on the voltage of the battery 18 and on the voltage of the line 2. Current starts between the cathode 8 and anode 9 at an instant of time dependent on the voltage of the line 2.

Thus if the voltage of the line 2 is slight- 1y above its normal value, the voltage a plied to the grid 6 has a magnitude in icated by the curve '27, the resultant potential of the grid is negative at the instant t, when the. potential of the anode 9 becomes positive, current does not start between the cathode 8 and the anode 9 until the instant 27 when the resultant grid potential becomes positive, the excitation of the machine 1 is decreased, and the voltage of the line 2 tends to decrease to itsnormal value. If thevoltage of the line 2 decreases slightly below its normal value, the voltage applied to the grid 6 has a magnitude indicated by the curve 27 the resultant potential of the grid 6 ispositive at the instant t when the potential of the anode 9 becomes positive, current is transmitted between the cathode 8 and anode 9 throughout the entire half cycle of anode voltage, the excitation of the machine 1 is increased, and the voltage of the line 2 tends to be restored to its normal value. Variation of the line voltage from .device through .one

' its normal value thus produces successive minimum and maximum Values of field excitatioii which are averagedin a manner to maintain this voltage within narrow limits.

Fig. 3 shows an exciter bus 29 which is urrangedto supply current to the field W1nd lugs 30 of the exciters 31 and is connected to the circuit 2 through the valve 5 and the transformer 4. Y In this embodiment of the invention, the rids 6 and 7 areconnected to the cathode 8 through a resistor 32, a direct current source 33 and opposite halves of the secondary circuit of a transformer 34 which has its primary winding 35 connected to the circuit 2 through phase control means shown as a condenser 36 and a resistor 37. It will be observed that the resistor 32 is connected to a current supply means 38 through a space discharge device 39, and that the cathode of the device 39 is connected to the grid of this phase of the circuit 2 and a grid leak device comprising a'condenser 40 and a resistor 41.

The operation of the apparatus illustrated b by F 1g. 3 will be explained by reference to Fig. 4 wherein the potential of the anode 9 is represented by the curve 26, different values of the potential applied to the grid 6 through the transformer 34 are represented by the curves 27, 27 and 27 the positive has potential applied to the grid 6 by the source 33 is represented by the line 42 and diiferent values of the resultant positive bias potential applied to the grid 6 through the source 33 and the resistor 32 are indicated by the lines 43, 44 and 45. The phase relation between the potentials ofgrid 6 and anode 9 is dependent on the adjustment of the condenser 36 and may be assumed to be that indicated by Fig. 4.

en the voltage of the circuit 2 is normal, the resultant grid potentialcomprises an alternating voltage represented by the curve 27 and a resultant positive bias potential represented by the line 44. Under these conditions, the resultant bias potential applied to the id 6 at the instant t when the voltage of t e anode 9 becomes positive is substantially zero and current will start be tween the cathode 8 and the anode 9 either at the instant t or the instant I), depending on whether the voltage of the line 2 is slightly hi her or lower than its normal value.

f the line voltage decreases below its normal value, the alternating component of the id potential is decreased as indicated by t e curve 27 and the resultant positive bias potential is decreased to a value repre sented by the line 43 due to the decrease in the current transmitted to the resistor 32 through the valve 39. Under these conditions, the resultant'potential of the grid 6 is positive at the instant t when the volta of the anode 9 becognes positive, current 1s transmitted between the cathode.8 and the anode 9 during the entire positive half cycle of anode voltage, the excitation of the machines 1 is increased, and the voltage of the line'2 tends to be increased to its normal value. As the voltage of the line 2 increases, the positive bias potential applied to the grid 6 through the resistor 32 also increases and the tendency to hunting is obviated or greatly reduced because of the fact that the anode current is caused to start at the instant t if the alternating component potential at any time exceeds the positive bias potential when the anode volta e becomes positive.

If the line v'o tage increases above its normal value, the alternating voltage of the grid is increased to a value indicated by the curve 27", the positive bias potential or" the grid is increased to a-value represented by the line 45, the resultant potential of the grid 6 is negative at the instant t when the anode voltage becomes positive, current starts be tween the cathode 8 and the anode 9 at the instant 25 when the resultant grid potential ecomes positive, the excitation of the machines 1 is decreased, and the line voltage tends to be decreased to its normal value. As the voltage positive bias potential applied-to the grid through the resistor 32 also decreases but the resultant positive bias potential of the grid is always maintained at a value fairly close to that of the alternating component of the grid potential so that hunting, due to the line voltage swinging below and above its normal value, is prevented.

Slight variations in the line voltage thus cause a series of maximum and minimum corrective efiects which are produced both without hunting and without appreciable time delay and are so averaged to maintain the line voltage within very narrow limits.

The embodiments of the invention illustrated and described herein have been selected for the purpose of clearly setting forth the principles involved. It will be apparent, however, that the invention is susceptible of being modified to meet the difierent conditions encountered in its use and I therefore aim to cover by the appended claims all modifications within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is,-;

- 1. A regulating apparatus comprising an electrical valve provided with a grid arranged to control the current transmitted between its cathode and anode, means operable to control the phase relation between the voltages of said grid and said anode, and means for biasing said grid to a positive potential.

2. The combination of an electrical valve comprising a grid arranged to control the current transmitted between its cathode and of the line 2 decreases, the

anode, means operable to control the phase relation between the voltages of said grid and said anode, and means arranged to apply to said grid a positive bias potential which varies in accordance with the voltage of said anode.

3. The combination of an electrical valve comprising a grid arranged to control the current transmitted between its cathode and anode, means operable to control the phase relation between the voltages of said grid and said anode, means for biasing said grid to a positive potential, and means for applying to said grid a bias potential which-varies in accordance with the voltage of said anode.

4. The combination of an electrical valve comprising a grid arranged to control the current transmitted between its cathode and anode, means operable to control the phase relation between the voltages of said grid and said anode, a direct current source arranged to apply a bias potential to said grid,

and means arranged to apply to said grid a positive bias potential which varies in accordance with the voltage of said anode.

5. The combination of an electrical valve comprising a grid arranged to control the current transmitted between its cathode and I anode, a circuit subject to unstable operating conditions when its load exceeds a predetermined value, asynchronous machine provided with an armature winding connected to said circuit and with a field winding connected .to said circuit through the cathode and anode of said valve, and means for applying to said grid a bias potential which varies in accordance with an electrical condition of said circuit.

6. The combination of an electrical valve comprising a grid arranged to control the current transmltted between its cathode and anode, a circuit subject to unstable operating conditions when its load exceeds a predetermined value, a synchronous machine pro= vided with an armature winding'connected to said circuit and with a field winding connected to said circuit through the cathode and anode of said valve, means for applying a substantially constant bias potential to said grid, and means for applying to said positive bias potential which varies 1n accordance with the voltage of said circuit.

In witness whereof, I'have hereunto set my hand this 28th day of October, 1926.

ALBERT H. MITTAG.

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